Push-off cap of plastic

ABSTRACT

A guarantee strip via break-off webs is integrally formed on a push-off cap with a cover surface and with a peripheral skirt on which a push-piece is arranged. This guarantee strip is designed without tabs as a closed ring. In order to be able to open the push-off cap with one hand, according to the invention it is suggested to vary the break-off webs in diameter. At the same time in particular the break-off webs in the region of the push-piece are designed thinner than the break-off webs which are arranged subsequent to these. The extremely thin break-off webs, to prevent injury when placing on [the cap], are protected by way of support cams which are arranged in the intermediate space between the lower edge of the peripheral skirt and the upper edge of the annular guarantee strip, so that only a very narrow gap arises.

BACKGROUND OF THE INVENTION

The present invention relates to a push-off cap of plastic for fasteningon a container with a container neck with a retaining bead, wherein thecap comprises a peripheral skirt on which a push-piece is integrallyformed and on which a peripheral guarantee strip engages via break-offwebs.

Here it is the case of closures which are placed onto relativelywide-necked, thread-free containers and are held on the container neckwith a positive and/or non-positive fit, wherein the container neck hasa suitable peripheral retaining bead. Such a closure is already knownfrom the Swiss patent CH-207 849 A with which the cap comprises aperipheral wall with which a tab for tearing off is integrally formedand a peripheral guarantee strip is integrally formed via a break-offseam. These early closures are still formed of metal. Versions in asimilar constructional shape which are manufactured of plastic havehowever already been known for quite some time. Thus U.S. Pat. No.3,707,240 discloses a push-off cap of plastic which may be fastened on acontainer neck with a retaining bead with a positive and with anon-positive fit, and additionally, for an improved sealing andmounting, is provided with a sealing plug engaging into the containerneck. This closure is furthermore provided with a peripheral guaranteestrip and at the location of the connection comprises a peripheralbreak-off seam. The guarantee strip comprises a tear-open tab but ishowever designed as a closed ring, but in the region of the tabcomprises a break-off location running vertically to the peripheralbreak-off seam in the mentioned region. A similar solution, but withoutthe mentioned sealing plug is known from U.S. Pat. No. 3,860,137.

Only with the further development of the shape design did then push-offcaps of plastic appear which as an integrity guarantee comprisebreak-off seams in the form of break-off webs in the region of thepush-piece. A tear seam which is perforated at a later stage forms thesebreak-off webs. Such closures for example are known from the Swisspatent CH-A-417 378 or from U.S. Pat. No. 3,899,097.

During further development, the majority of push-off caps have beenreplaced by snap-hinge closures. Here, as also with the rotationclosures, the guarantee strips were integrally formed via break-offwebs. In order to be able to manufacture these closures one requiresrelatively complicated tools which were developed only during theeighties of the last century. On the one hand the injection moulds withstar-shaped mould slides were used and later also moulds withcollapsible cores and finally injection moulding tools with insertsfashioned in the manner of chucks which engage around the cap from theoutside during the injection procedure and widen elastically outwards onremoval from the moulds.

Push-off caps of plastic of the initially mentioned type may be obtainedtoday on the market. The guarantee strips at the same time comprise atab and an opening or break-off location present in the region of thetab. For opening a container with such a push-off cap one requires bothhands. The container is held with one hand whilst the other hand gripsthe tab and thereafter the guarantee strip is torn off. Once theguarantee strip has been removed, the push-off cap may be opened withone hand by way of exerting a force onto the push-piece with the thumb,and the cap is elastically deformed and is pressed away past theretaining bead on the container neck.

It is known that during the manufacture of a plastic closure, the chainmolecules of the plastic align themselves longitudinally in thebreak-off webs during the injection procedure. At the same time, thedestruction of the break-off webs by way of tension in the direction inwhich the break-off webs run requires considerably more force than adestruction by a force which occurs perpendicular to the direction inwhich the break-off webs run and thus occurs perpendicularly to themolecule chains. This problem has been scaled down with rotationclosures. With rotation closures a force multiplication is effected viathe thread, by which means the required forces may be mustered despitepractically all break-off webs being destroyed simultaneously. Withpush-off caps the forces are applied on one side in the region of thepush-piece, but despite this the required forces until now have been solarge that a controlled opening has not been able to be realised.

It is therefore the object of the present invention to realise apush-off cap of the initially mentioned type which may be opened withhand.

BRIEF DESCRIPTION OF THE INVENTION

A push-off cap with the features of patent claim 1 achieves this object.

BRIEF DESCRIPTION OF THE DRAWINGS

Thanks to the new concept of varying the break-off webs along theperiphery, one may achieve different opening functions. With regard tothis, the subsequent description is referred to in which the inventionis described in detail with reference to the drawings. The drawings showone preferred embodiment of the subject-matter of the invention by wayof which solutions which differ from this are hereinafter explained indetail. There are shown in:

FIG. 1 a lateral view of the push-off closure with a view onto thepush-piece and

FIG. 2 the same view of the push-off cap rotated by 90°.

FIG. 3 shows the plan view of the push-off cap.

FIG. 4 represents a diametrical vertical section through the capaccording to FIG. 2 along line A-A in an enlarged scale, whilst

FIG. 5 shows a horizontal section along the line B-B according to FIG.2, with a view into the inner side of the push-off cap whilst omittingthe guarantee strip.

FIG. 6 shows the enlarged detail D, as specified in FIG. 5 and

FIG. 7 the detail C according to FIG. 4 in an enlarged scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The complete push-off cap consists essentially of two elementsmanufactured as one piece, specifically the actual push-off cap 1 andthe guarantee strip 2 which is connected to this as one piece. Theactual push-off cap 1 consists of an upper cover surface 3 and aperipheral skirt 4 which connects to this. A push-piece 5 is integrallyformed on the skirt 4. The push-piece has an actual push surface 10which projects perpendicularly from the skirt and is held on the skirt 4reinforced by support ribs 9.

The guarantee strip is realised as a closed ring and is connected to theskirt 4 of the push-off cap 1 via break-off webs 6. An elongate supportcam 7 is integrally formed on the skirt between in each case twoadjacent break-off webs 6. A thin free gap 8 remains between theelongate support cam 7 and the guarantee strip 2. The support cams areso long that they fill out almost the entire intermediate space betweenin each case two adjacent break-off webs 6. The break-off webs 6 whichaccording to the invention are extremely thin would be destroyed per seif on placing on, the guarantee strip 2 were not to lie on the supportcams. On placing the push-off cap on the container neck, the break offwebs despite this are slightly compressed together. On placing on thepush-off cap, a retaining bead 11 must be pressed over a correspondingretaining bead on the container neck so that these two retaining beadsmutually engage behind one another with a positive fit.

The actual push-off cap 1 is additionally held on the container neckwith a second retaining bead 12 which is integrally formed on the innersurface of the peripheral skirt 4. Instead of a retaining bead it wouldalso be of course possible to realise the connection with suitableretaining cams. This second retaining bead in the example representedhere does not cause this to assume a sealing function. With this, on theinner side of the cover surface 3 an annular wall is arrangedconcentrically to the peripheral skirt 4 and forms the sealing plug 13.

In FIG. 5, all break-off webs 6 are characterised by the letters a-l.Thanks to the present invention a simple solution has been found to beable to change the function of the push-off cap by varying the diameterof the break-off webs. For the one-handed opening on which the object ofthe invention has been based, it is important for the break-off webs inthe region of the push-piece 5 to be able to be destroyed withrelatively little effort. Accordingly, the two break-off webs g and h attheir break-off location are reduced to a diameter which is smaller thanthe diameter at the break-off locations of the other break-off webs.This is due to the fact that the introduction of force in the region ofthe push-piece runs practically in the running direction of thebreak-off webs. In this direction, the break-off webs due to thearrangement of the chain molecules are very resistant since herepractically a pure tensile force occurs. With the webs with lie furtherto the side, the introduction of force, created by a certain deformationof the cap, is effected by way of a combination of a tensile and shearforce. Added to this is also the fact that the lever ratios always havea more favourable effect. Accordingly, the diameter of the break-offlocations c-f and i-l is selected larger than the diameter of thebreak-off webs g and h. With the break-off webs a and b the conditionsare again unfavourable and accordingly one would advantageously designthe break-off webs a and b likewise smaller in cross section than thebreak-off webs c-f and i-l.

According to experience the break-off locations may be varied in theregion between 0.05 mm and 0.4 mm depending on the selection ofmaterial. These details concern in particular the selection ofpolypropylene or polyethylene which have both been shown to be suitablefor push-off caps. Other plastics however are in no way excluded.Typically, the diameter of the break-off webs in the region of thepush-piece lie in the magnitude of 0.05 mm and 0.25 mm. Most preferablyhowever the diameter would rather tend towards the lower region,specifically in the region between 0.07 mm and 0.15 mm. With theselection of this diameter of the break-off webs in the region close tothe push-piece one would therefore prefer to select the break-off websc-f and i-l in the upper region, specifically with diameters of 0.2 mmto 0.4 mm. In contrast to this the break-off webs which are arrangeddiametrically opposite the push-piece are selected in a magnitude ofbetween 0.1 mm and 0.3 mm, more preferably however between 0.15 mm and0.25 mm. All previously mentioned dimensional details are of coursedimension recommendations which must be seen in relation to the push-offcap. With push-off caps with considerably larger diameters, break-offwebs with larger diameters are of course also considered.

If such push-off caps are attached to larger receptacles, then it may bedesirable to easily be able to place the push-off cap back onto thecontainer again. This with a design according to the invention may berealised by way of increasing the break-off webs a and b in diameterwith respect to the other break-off webs. In this case the break-offwebs then serve as joints. With normal one-handed operation these twowebs a and b are no longer severed and the closure remains hanging onthese two webs. Since furthermore the guarantee strip is designed as aclosed ring, this remains on the bottle and accordingly the push-off capwith the previously mentioned design shape remains fastened on theguarantee strip and thus indirectly also on the bottle. Thus thepush-off cap according to the invention may be converted into a push-offcap with a so-called flap closure with little effort.

As is particularly evident from the FIGS. 6 and 7, the break-offlocations are preferably formed in a conical manner. This conicalshaping leads to the fact that the actual separation location orbreak-off location of the break-off webs 6 may be applied exactly towhere this is desired. In the present case the break-off location whichis indicated at 14 is applied directly on the connection location on theguarantees strip 2. It is ensured by way of this that the remainder ofthe webs remain on the skirt 4. This is selected because such closuresare often attached onto relatively small bottles which are applieddirectly to the mouth in order to drink from this. The lips thereforewould come into contact with the guarantee strip remaining on thecontainer neck and a certain danger of injury would not be ruled out ifthe remainder of the severed break-off webs 6 were to remain on theguarantee strip.

In the present case the invention is particularly explained by way of around closure. Basically however one may also shape the push-off caps inan oval manner or also in other shapes. If the shapes of a push-off capdeviate from the round shape, then on opening also different forceconditions and other lever effects occur and accordingly the crosssections of the break-off webs may be adapted to these conditions.

The precision required for this is unusual for a push-off cap whichindeed belongs to the most economical variant of plastic closures.Despite this, the reason why this may still be realised lies in the factthat for the manufacture here, one has employed injection moulds withchuck-like inserts. This technology per se is also unusual for plasticclosures in this price class.

One may only realise the extraordinarily fine connection locations andbreak-off webs with a high processing safety thanks to the use ofchucks. This high processing safety leads to a high economicabilitydespite the relatively expensive injection moulds.

1. A push-off cap of plastic for fastening on a container with acontainer neck with a retaining bead, wherein the cap comprises aperipheral skirt on which a push-piece is integrally formed and on whicha peripheral guarantee strip engages via break-off webs, characterisedin that the guarantee strip is designed completely and without tabs asan unweakened closed ring and is integrally formed via break-off webs,wherein the break-off webs have different diameters and on account ofthis permit a one-handed opening of the cap for the first time.
 2. Apush-off cap according to claim 1, characterised in that the break-offwebs in the vicinity of the push-piece have a smaller diameter than thebreak-off webs which follow directly in the peripheral direction.
 3. Apush-off cap according to claim 1, characterised in that the break-offwebs in the region lying diametrically opposite the push-piece have asmaller diameter than the adjacent break-off webs.
 4. A push-off capaccording to claim 3, characterised in that the break-off webs in theregion lying opposite the push-piece have a larger diameter than thebreak-off webs in the region of the push-piece but a smaller diameterthan the adjacent break-off webs.
 5. A push-off cap according to claim2, characterised in that at least one connection location between theguarantee strip and the cap is present diametrically opposite thepush-piece, and this location forms a joint for reclosure of the cap. 6.A push-off cap according to claim 1, characterised in that the break-offwebs reduce in cross section from the cap skirt towards the guaranteestrip.
 7. A push-off cap according to claim 1, characterised in that thebreak-off webs reduce in cross section from the guarantee strip towardsthe skirt.
 8. A push-off cap according to claim 1, characterised in thatbetween in each case two adjacent break-off webs on the skirt there areformed support cams which reach down to approximately on the upper edgeof the guarantee strip.
 9. A push-off cap according to claim 1,characterised in that this is manufactured without a mould slide by wayof a chuck.
 10. A push-off cap according to claim 1, characterised inthat the break-off webs with regard to their smallest diameter varybetween 0.05 mm and 0.45 mm.
 11. A push-off cap according to claim 2,characterised in that the break-off webs in the region of the push-piecehave a minimum diameter between 0.05 mm and 0.25 mm, more preferablybetween 0.15 mm and 0.25 mm.
 12. A push-off cap according to claim 3,characterised in that the break-off webs in the region lyingdiametrically opposite the push-piece have a minimum diameter between0.2 mm and 0.45 mm, more preferably between 0.25 mm and 0.35 mm.
 13. Apush-off cap according to claim 8, characterised in that the distancebetween the lower edge of the support cams and the upper edge of theguarantee strip lies in the region between 0.15 mm and 0.25 mm.